Rectifying device



Nov. l, 1938.

T. JURRIAANSE RECTIFYING DEVICE n g--fgf Filed April 19, 1957 [ALTPatented Nov. 1, 1938 PATENT ogFfFlcE nEo'riFYING DEVICE TomJurriaansaEindhoven, Netherlands, assignor -to N. V. Philips,Gloeilampenfabriekem Eindhoven, Netherlands Application April 19, 1937,SerialNo'. 137,851 VIn Germany April 21, 1936 My inventionrelates to-A.C. rectifyingdevicea and more particularly to devices Vcomprising anincandescible-cathodeionic rectifying tube.

My invention 'is particularly advantageous rin connection with therectication of A. C current of medium voltages-having an inversepeakyalue of about 150-1000 volts-and'foi` currents of -from severalamperesto 100 amperes Yormore; howe ever it is Vnot limited theretmbutmay beu'sed'in connection with other-voltages and currents.v

It is, of course, essentialto prevent back discharges in gaseousrectifying -tubes,"i. e; tubes having a filling of one or more gases,vapors, or a mixture thereof, and much'worli` has been done in thisdirection, especially in connection withmercury-eatl1ode tubes. Althoughthe use of a gaseous lling at low pressure, for instance 0.01 mm. of Hgor less, will prevent such discharges, this results in a very highvoltage drop in the discharge path, which reduces the life of the tube.More particularly, in incandescible-cathode tubes, the life of thecathode is materially reduced by ionic bombardment due to the `highvoltage drop in the discharge path, and the cathode had to be madeoversize to ensure reasonably long life. On the other hand, if the llingis given a high pressure, for instance 1 mm. of Hg Vor more, to-

the gaseous filling has generally been given a` compromise value whichfully met the essential condition 'of preventing back -discharges at theexpense of a reduced life of the tube.

The object of my invention is to eliminate the above difliculties and toremove the undesirable eiiect of a low-pressure filling upon the -liieof the tube, while retaining its protective effect against backdischarges.

In accordance with the invention, I use -an incandescible-cathoderectifying tube having `a. gaseous filling at a pressure of less than0101 mm. of Hg even at the emitting surface of the cathode, and providewithin the tube a magnetic eld whose lines of force connect the anodeand cathode. Y

With such a construction the protection against back discharges 4is notappreciably reduced,` whereas the possibility-ot ionizationl for thedischarge is greatly increased in the direction of current flow; dueprobablyto the extension of the ,electron paths through the magneticfield wherebyithe'possibility of.;e1ectrons colliding with neutral; gasI.moleculesorV gas`4 `atoms is` .greatly (Cl. Z-27.5)

increased. This appears from the fact that there is a decrease in thecathode drop whereby the disintegration of the cathode is reduced andthus the life of the tube'is materially increased. As the cathode kdropgenerally constitutes the mainportion of the total voltage drop of thedischarge, thus phenomenon is of especial importance.

It is preferable that the discharge path follow as closely as possiblethe lines of forcev of the magnetic field, as I have found that aconsiderably larger voltage drop will occur in .the discharge at anypoint at which the path is caused to deviate from the magnetic lines offorce. Furthermore, I prefer to so arrange the electrodes in themagnetic field that substantially the entire discharge path extendswithin that part of the discharge space which is traversed by themagnetic lines of force. In this manner the efliciency of thearrangement is increased to' the maximum, whereas ami-nimum amount` ofmagnetic energy is required.

In one embodiment of my invention, as applied to a full-wave rectifyingtube, I so arrange the magnetic eldthat the' lines of force traverse thetube envelope at two definite points at which the anodesare disposed,whereas I locate the cathode in the center of the magnetic beamextending between these points, so that the discharge path extends inthe direction of the magnetic lines of force. In such arrangement themeans for producing the magnetic eld can be Very advantageously providedoutsideof the tube, and the magnetic eld can be readily concentrated atthe desiredV points of the envelope.

In order that my invention maybe clearly understood and readily carriedinto effect, I shall describe same more ful-ly with reference to theaccompanying drawing, in which:

Figures 1 and 2 are partly sectionized views of full-wave rectifyingdevices according vto the invention. t

The device illustrated in Fig. 1 comprises a full-Wave rectifying tube3, a permanent magnet 5, and a rectifying circuit arrangement indicatedby 4 and having single-phase A. C. supply terminals and D. C. outputterminals.

The tube 3 comprises a closed envelope 8 of vitreous material, anincandescible cathode I, energized in asuitable manner -not shown, andtwo anodes 2 in the form of metal discs, Afor instance of iron, adjacentthe envelope.- Cathode I- and anodes2 are connected to arrangement 4 bymeans of conductors!! to I2, and as such rectifying. circuits are Well'known' in the art,

further description of same is believed unneces- Sary.

Tube 3 is provided with a suitable gaseous lling, for instance mercuryvapor, having during operation a pressure of less than 0.01 mm. of Hg.As shown, a quantity of mercury I3 is provided in a protuberance, formedpreferably in a cool portion of the envelope. In some instances it ispreferable to artificially cool the portion of the envelope in which themercury is disposed, for instance by a circulating cooling liquidjinorder to maintain the mercury at a temperature which agrees with thecorresponding saturation pressure of the mercury vapor within the tube.As such cooling means are well known in the art and do not form part ofthe present invention, further description or illustration of same isbelieved tobe unnecessary."

Disposed outside tube 3 with its pole faces in contact with the outersurface of envelope 8 and in line with anodes 2, is a permanent magnet5. Magnet 5 produces a constant magnetic field whose lines' offorce'extend within the tube be-` tween anodes 2, as indicated by thearrowed lines 6. It will be noted that cathode I is disposed centrallywithin this magnetic field, and that the discharge path between cathodeI and anodes 2 closely follows the lines of force of this field. i

It will be noted that cathode I extends perpcndicularly to the lines offorce, and thus is intercepted by a maximum number of lines of force,which insures a .minimum voltage drop of the discharge. Furthermore, thelines of force extending between the anodes 2 are located in a spacewhich is materially free from any obstruction which might impede thepassage of the discharge along the lines of force extending from thecathode to each anode.

To prevent the possibility of back discharges being caused by particlesdisintegrating from cathode I and dropping on the anode 2, a screen I ofnon-magnetic material such as molybdenumV intercepts straight linesdrawn from any point on the cathode to the anodes. Two such lines areindicated by I5. v Y,

'It will be noted that the screen 'I is curved to follow the directionof therlines of force, and` thus intercepts only a Yminimum number ofthel lines.

Although in Figure 1 a constant magnetic field as produced by apermanent magnet has been shown, an electromagnet may also be used. Thisis shown in Figure 2 in which the same reference numbers have been usedto designate the parts corresponding to those of Figure 1.

In contradistinction to Figure 1 the anodes 22 are not supported byseparate anode supports but they are directly welded to circularferrochromium discs I6 forming part of the envelope 23 of the tube. Thetwo legs I'I ofthe electromagnet are welded to the discs I6 and serve atthe same time as lead-in conductors to theanodes 22. The magneticcircuit is completed by pole pieces I8 having a gap I9 between themwhich prevents the setting up in the glass envelope of thermal stresseswhich might damage` the tube and insulates the two anode leads from eachother. v

The electromagnet windings are connected to a current supply 20 shown`schematically and providing the electromagnet with direct oralternating vcurrent according as to whether a constant or a pulsatingmagnetic eld is desired.

In fact it is immaterial invvhatr direction the magnetic eld maypulsate, provided it disappears only at the moments at which it can bedispensed with for suitable operation 'of the tube.

Y Under some conditions it is of advantage to use a magnetic field whichpulsates with the anode'current in such a manner that the magnetic fielddisappears during the blocking phase of the Yanode and thereby insuresmaximum protection against back discharges.

The tubes shown in the figures of the drawing may be used to rectifyalternating currents up to rof the order of 1-50 ampere at negative peakvoltages of approximately 150 volts or higher.

While I have described my invention in connectionuwith specific examplesand applications, I do not wish to be limited thereto but desire theappended claims to be construed as broadly as permissible in view of theprior art.

What I claim isz- 1. A full-wave rectifying device comprising an ionicdischarge tube having an envelope, an incandescible cathode, two anodesdisposed adjacent the wall of the envelope, and a gaseous llf ing havingduring operation a pressure less than 0.01 mm. of mercury, and meansoutside the envelope to produce a magnetic field having lines of forcetraversing the envelope at points adjacent the anodes and extendingbetween the anodes in a beam, said cathode'being centrally disposedwithin said beam and spaced from said anodes to form a discharge pathfollowing the lines of force thereof.

2. A'full-wave rectifying device comprising an ionic discharge tubehaving an envelope, an incandescible cathode having amain emissionsurface, two anodes disposedV adjacent the wall of the envelope, and agaseous filling having during operation a pressure less than 0.01 mm. of mercury, and means outside the envelope for producing a magnetic fieldhaving lines of force traversing the envelope at points adjacent theVanodes and extending between the anodes in a beam, said cathode beingcentrally disposed within said beam with the main emission surfaceextending transversely to lines'of force thereof and being spaced fromsaidranodes to form a Vdischarge path following the lines of force.

3. A full-wave rectifying device comprising an ionic discharge tubehaving an envelope, an incandescible cathode, two anodes disposedadjacent the wall of the envelope, and a gaseous filling having duringoperation a pressure less than 0.01 mm. of mercury, and means outsidethe envelope to produce a magnetic eld having lines of force traversingthe envelope at points adjacent the anodes andextending between theanodes in a beam, said cathode being centrally disposed within said beamand spaced from said anodes to form a discharge path following the linesof force thereof and lying substantially entirely'within the portion ofthe discharge space traversed by the lines of force.

4. A full-wave rectifying device c'omprisingan ionic discharge tubehaving an envelope, an in candescible cathode, two anodes Ydisposedadjacent the wall of the envelope, said cathode being spaced from eachanode by a distance substantially equalv to the distance between theanodes,

a screen between said cathode and anodes and lo,

cated symmetrically with respect to'a line passing through said anodes,and a gaseous filling having during operation a pressure less than 0.01mm. of mercury, and means outside the envelope to .produce a mageticfield having lines of force traversing the envelope at points adjacentthe anodes and extending between the anodes in a beam, said cathodebeing centrally disposed within said beam to form a discharge pathfollowing the lines of force thereof.

5. A full-wave rectifying device comprising an ionic discharge tubehaving an envelope, two anodes disposed adjacent the wall of theenvelope and substantially in a common plane, an incandescible cathodedisposed above said plane and symmetrically with respect to said anodes,a screen between said cathode and said plane and located symmetricallywith respect to said anodes, said screen intercepting a straight linebetween any point on said cathode and any point on said anodes, and agaseous lling having during operation a pressure less than 0.01 mm. ofmercury, and means outside the envelope to produce a magnetic eld havinglines of force traversing the envelope at points adjacent the anodes andextending between the anodes in a beam, said cathode being centrallydisposed within said beam and spaced from said anodes to form adischarge path following the lines of force thereof.

6. A full-wave rectifying device comprising an ionic discharge tubehaving an envelope, two anodes disposed adjacent the wall of theenvelope and substantially in a common plane, an incandescible cathodedisposed above said plane and symmetrically with respect to said anodes,a screen between said cathode and said plane and located symmetricallywith respect to said anodes, and a gaseous filling having duringoperation a pressure less than 0.01 mm. of mercury, and means outsidethe envelope to produce a magnetic field having lines of forcetraversing the envelope at points adjacent the anodes and extendingbetween the anodes in a beam, said cathode being centrally disposedwithin said beam and spaced from said anodes to form a discharge pathfollowing the lines of force thereof, said screen being curved to followthe lines of force.

7. A discharge tube having electrodes including a cathode, and anenvelope having a vitreous portion and metal members sealed therein, andmeans for producing a magnetic eld within said envelope comprising acoil and a core 'having two portions insulated from each other, each ofsaid portions having one end secured to one of said members.

8. A full-wave rectifying device comprising an ionic discharge tubehaving an envelope comprising a vitreous portion and two metal memberssealed therein, an incandescible cathode, two anodes each secured to oneof said metal members, and a gaseous filling having during operation apressure less than 0.01 mm. of mercury, and means outside the envelopefor producing a mag netic eld having lines of force passing through saidmetal members and anodes and extending between the anodes in a beam,said cathode being centrally disposed within said beam and spaced fromsaid anodes to form a discharge path following the lines of force, saidmeans comprising a coil, and two cores electrically insulated from eachother, each core having one end secured to the outer surface of one ofsaid metal members.

TOM JURRIAANSE.

